How to move only a vertex at a time of an empty object with an image sequence attached
If you want your reference image to align with the camera, setup the camera to use a background image.

In 2.80 Background Image options have been added to the camera, this allows you to keep the image aligned with the camera view even if you move the camera.



To ensure the image fills the camera view you need to set the render resultion to match the aspect ratio of the reference image.